1. Field of the Invention
This invention relates to the production of immortalized cell lines from avian T lymphocytes, and the use of those cell lines to produce immune lymphokines.
2. Description of the Prior Art
Earlier studies have shown that Salmonella enteritidis (SE)-immune chicken T cell lymphokines from non-transformed cells (SEILK) are efficacious against experimental SE infections in 1-day-old and 18-day-old leghorn chicks (McGruder et al., 1993, Poultry Sci., 72:2264-2271, and Tellez et al., 1993, Avian Dis., 37:1062-1070). When these lymphokines (SEILK) were administered intra peritoneally (i.p.) to chicks thirty minutes before SE challenge, protection against SE organ invasion occurred within 24 hr. However, when lymphokines from normal, non-immune avian T cells were administered prophylactically, protection against SE organ invasion was not observed (McGruder et al., 1993, and Tellez et al., 1993, ibid). The increased resistance to infection seen with SEILK administration is characterized by a heterophilic inflammatory influx into the peritoneal cavity which peaks at 4 hr after challenge injection. Heterophils isolated from SEILK injected chicks displayed increased inflammatory reactivity when tested in vitro for adherence, chemotaxis, phagocytosis of SE, and killing of SE, S. typhimurium, S. gallinarum, and Escherichia coli as compared to heterophils from saline injected control birds (Kogut et al., 1995, J. Leuk. Biol., 57:56-62). Hypothetically, SEILK injection induces a heterophilia and activation of these cells while the invasive process of the SE provides the secondary signal for the site of the inflammatory response resulting in increased phagocytosis and killing of the invading organism. Consequently, there is a greatly reduced bacterial invasion into the parynchymal organs.
To date, all studies utilizing SEILK have involved the tedious task of repeatedly making batches of SEILK from hyperimmunized chickens for continued experimental use. Viral transformation has been demonstrated with human T cell clones using Herpesvirus saimiri (Weber et al., 1993, Proc. Natl. Acad. Sci. USA, 90:11049-11053), producing immortal cells which are easy to grow in culture. Recently, retroviral transformation in vitro of chicken T cells has been demonstrated using the reticuloendotheliosis virus strain T (REV-T). REV-T, a replication defective avian retrovirus, transforms avian hematopoietic cells due to the integration of the oncogene, v-rel, into the host cell genome (Hoelzer et al., 1979, Virology, 93:20-30, and Stephens et al,. 1983, Proc. Natl. Acad. Sci. USA, 80:6229-6233). When the helper virus chicken syncytial virus (CSV) is introduced, virus particles are produced that are tropic but not cytopathic for transformed lymphocytes (Barth and Humphries, 1988, J. Exp. Med., 167:89-108). B cells are transformed exclusively when ex vivo spleen cells are exposed to REV-T(CSV) transformation, while pre-mitogen stimulation of spleen cells yield predominantly transformed T cells (Marmor et al., 1993, J. Exp. Med., 177:647-656; and Schat et al., 1992, Avian Diseases, 36:432-439). However, the transformation of the T cells was only short term. Apparently, the transformed T-cells were not truly immortal, but required the addition of exogenous interleukins to maintain growth (Marmor et al., ibid).